1. Field of the Invention
The present invention relates to a burn-in apparatus for operation of semiconductor integrated devices under normal or extreme condition, prior to actual use.
2. Description of the Related Art
In order to assure the quality and reliability of semiconductor integrated device, it is absolutely necessary to conduct a so-called burn-in, which is a screening test under high temperature in order to stabilize its characteristics and eliminate early failures, before shipment. The burn-in system can be classified into the following three types according to the operating condition of a semiconductor integrated device under test.
a. Static burn-in system: there is provided with a pyrostat and a DC power supply, and a constant voltage is applied to the semiconductor integrated devices in the pyrostat from the DC power supply.
b. Dynamic burn-in system: the dynamic system further comprises a pulse generator for imitating an operation of the device under actual use. A constant voltage is applied to the devices in the pyrostat from the DC power supply and a signal close to an actual operating state is input to the semiconductor integrated devices from the pulse generator.
c. Monitored burn-in system: the system has a monitoring function for measuring continuously or at intervals output signals from the semiconductor integrated devices in a dynamic burn-in, and then an accept-reject decision is made to eliminate devices with a defect during the burn-in.
In such a burn-in system, there is provided with a plurality of burn-in boards each having a connector for connecting with the DC power supply, the pulse generator or a monitor unit. A plurality of semiconductor integrated devices are accommodated in the sockets respectively, and the burn-in boards each having a plurality of semiconductor integrated devices are accommodated in the pyrostat for setting specified temperature and environmental conditions. For the monitored burn-in system, it is necessary to additionally provide a comparing and decision-making test device for making a pass-reject decision.
With the increasing number of pins, the progressing integration and the growing capability of the semiconductor integrated devices, the use of higher-function larger-scale burn-in equipment has become widespread and the investment in equipment for burn-in processes has been on the steady increase. Meanwhile, the trend toward the low-volume greater-variety production has been strengthened in recent years, and therefore, it is necessary to have various kinds of burn-in equipment to be ready for production of various types of semiconductor integrated devices. Above all, it is required to make ready a large variety of pyrostats so as to be meet different setting conditions for different types. The growing storage space and cost of the pyrostats have become no small problem.